By introducing injection liquid into a seabed formation, one is able, with the said liquid sample test, to choose the correct chemicals for blending with the injection water. If the injection water is not treated with the correct chemicals in the correct amount, the seawater within the seabed formation will react negatively with the injection liquid and form undesired salts etc. which are liable to clog bore holes and channels within the formation and thus seal them when the injection water is introduced from the surface.
Such liquid sample analysers are known as eleven-ion analysers, wherein a liquid sample is analysed with regard to eleven distinct parameters, e.g. content of sodium, potassium, magnesium, bivalent iron, calsium, strontium, barium, chlorides and sulphate, as well as the pH-value and electrical conductivity.
With this invention, the number of parameters is not restricted to precisely eleven; the parameter number may be greater or smaller. Thus, an eleven-ion analyser constitutes only one aspect of the invention.
There are no apparatus or instruments available on the market today which allow the determination of the above-mentioned element contents, chloride and sulphate contents, as well as the level of acidity and electrical conductivity, by means of one system based on a liquid sample injection and which allows analysis of all parameters under the same conditions (pressure/temperature).
For liquid sample analysis of the kind described above, the following known apparatus are used at present:
One system presently available is based on atomic absorption spectrophotometry, and another system is based on inductive plasma technique. Both comprise bulky, heavy instruments capable of analysing only some of the elements included in an eleven-ion analysis.
For each of these available instruments, a pH measuring device, a conductivity metering apparatus, an ion chromatograph or ion-selective electrodes or a spectrophotometer must be used as additional equipment. There is also the disadvantage with these techniques that the liquid samples have to be transported from the water source (which can sometimes be located far away) to a laboratory.
If one uses an analysis procedure based on the above-mentioned atomic absorption, the liquid sample has to be diluted in order to reduce the-concentration parameter to 1/1000 (one part per thousand). Such a dilution gives rise to substantial margins of error, and if, for example, 1000 tests were performed on this basis, the results might substantially very. Tests in such a number are performed routinely with the above-mentioned seawater or formation water analysis.
Therefore, one the present invention one has primarily aimed at eliminating or substantially reducing the difficiences, disadvantages and limitations in the available technique. This will provide a liquid sample analyser which achieves more accurate measurements. The conditions are optimized in order to obtain an accurate determination of, for example, the above-mentioned eleven parameters by means of a single system consisting of assembled components, on the basis of one single sample liquid injection, and where all the said parameters (more/less) are analysed under the same conditions.
The liquid sample analyser according to the invention, which is based on ion chromatography, is designed as a portable unit made up of easily assembled portable components, so that the analyser may be used in situ, i.e., the system can be installed at the source of the water to be analysed.
According to the invention, the above-mentioned aims are achieved by designing a liquid analyser in such a way that it demonstrates the features defined in the following claims.
Since the liquid analyser is based on ionchromatography, it is capable of treating and analysing undiluted liquid samples, thus avoiding the above-mentioned sources of error. An ion chromatograph determines which ions are present in a liquid sample as well as the consentrations of these ions.